Reflectors are generally used for electrooptical range finding or distance measurements. It has been found that reflectors can be inexpensively made from plastics, but such reflectors have the disadvantages that they deform and are therefore inaccurate. Therefore, such reflectors can only be used for very short ranges in electrooptical range finding.
Attempts have been made to produce reflectors from glass, which have a much better accuracy and can therefore be used for larger ranges in electrooptical range finding. However, such reflectors are expensive to manufacture.
Reflectors are also made from metal-plastics materials. These reflectors, known as hybrids, are produced by molding. Although they are more accurate than reflectors made from plastics alone, they are more expensive to manufacture than the latter.
The enumeration of known reflectors made from different materials show that accurate and precise reflectors can only be manufactured at great expense. It has therefore hitherto been necessary to accept certain disadvantages using expensive reflectors for longer ranges and cheaper reflectors for smaller ranges. There are no reflectors for medium ranges. The user is therefore forced to use very expensive reflectors for such medium ranges.
It is also pointed out that electrooptical range finding is used for the permanent monitoring of dams and glaciers, including avalanche-threatened areas. The need consequently exists for electrooptical range finding equipment which can be permanently installed at its point of use. However, this has not hitherto been possible because such equipment, particularly the reflectors, are much too complicated and therefore too expensive.